WLAN TDM protocol

ABSTRACT

A first wireless network device in a wireless network that includes a plurality of wireless network devices comprises an RF transceiver that transmits and receives data packets and that periodically transmits or receives a beacon. A control module communicates with the RF transceiver, determines a transmission position m and a default IFS time based on the beacon, selects a second IFS time when the RF transceiver receives a data packet from a second wireless network device having a transmission position m−1, and selects the default IFS time when the RF transceiver does not receive a data packet from the second wireless network device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application ser. No.______ (Attorney Docket No. MP0621), filed on Dec. 19, 2005. Thisapplication claims the benefit of U.S. Provisional Application No.60/645,520, filed on Jan. 18, 2005 and U.S. Provisional Application No.60/682,067 filed on May 18, 2005. The disclosures of the aboveapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to wireless networks, and moreparticularly to reducing power consumption of wireless network devicesand improving network utilization.

BACKGROUND OF THE INVENTION

IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11h, 802.11 n,802.16, and 802.20, which are hereby incorporated by reference in theirentirety, define several different standards for configuring wirelessnetworks and devices. According to these standards, wireless networkdevices may be operated in either an infrastructure mode or an ad-hocmode.

In the infrastructure mode, the wireless network devices or clientstations communicate with each other through an access point. In thead-hoc mode, the wireless network devices communicate directly with eachother and do not employ an access point. The term client station ormobile station may not necessarily mean that a wireless network deviceis actually mobile. For example, a desktop computer that is not mobilemay incorporate a wireless network device and operate as a mobilestation or client station.

A wireless network that operates in the infrastructure mode includes anaccess point (AP) and at least one client station that communicates withthe AP. For example, the wireless network may operate in aninfrastructure mode. Since the client stations are often batterypowered, it is important to minimize power consumption to preservebattery life. Therefore, some client stations implement a low power modeand an active, or “awake,” mode. During the active mode, the clientstation transmits and/or receives data. During the low power mode, theclient station shuts down components and/or alters operation to conservepower. Usually, the client station is not able to transmit or receivedata during the lower power mode.

Wireless network devices may be implemented by a system on chip (SOC)circuit that includes a baseband processor (BBP), a medium accesscontroller (MAC) device, a host interface, and one or more processors. Ahost communicates with the wireless network device via the hostinterface. The SOC circuit may include a radio frequency (RF)transceiver or the RF transceiver may be located externally. The hostinterface may include a peripheral component interface (PCI) althoughother types of interfaces may be used.

A power management device controls and selects different operating modesof the client stations. During operation, the power management deviceinstructs some of the modules to transition to a low power mode toconserve power. Additional information may be found in U.S. patentapplication Ser. Nos. 10/650,887, filed on Aug. 28, 2003, Ser. No.10/665,252, filed on Sep. 19, 2003, and Ser. No. 11/070,481 filed onMar. 2, 2005, which are hereby incorporated by reference in theirentirety.

Referring now to FIG. 1, a first wireless network 10 is illustrated inan infrastructure mode as defined by IEEE 802.11 and other futurewireless standards. The first wireless network 10 includes one or moreclient stations 12 and one or more access points (AP) 14. The clientstation 12 and the AP 14 transmit and receive wireless signals 16. TheAP 14 is a node in a network 18. The network 18 may be a local areanetwork (LAN), a wide area network (WAN), or another networkconfiguration. The network 18 may include other nodes such as a server20 and may be connected to a distributed communications system 22 suchas the Internet.

The client station 12 does not continuously transmit data to or receivedata from the AP 14. Therefore, the client station 12 implements a powersavings mode when the client station 12 and the AP 14 do not have datato exchange. Data commonly remains intact in a network for apredetermined amount of time before it is dropped. The incorporated IEEEstandards provide the opportunity for the client station 12 to informthe AP 14 when the client station 12 is entering a low power mode (andwill not be capable of receiving data for a predetermined period). Afternotifying the AP 14, the client station 12 transitions to the low powermode. During the low power period, the AP 14 buffers data that isintended to be transmitted to the client station 12. Following the lowpower period, the client station 12 powers up and receives beacontransmissions from the AP 14. If the beacon transmissions indicate thatthe AP 14 has data for the client station 12, or the host processor ofthe client station 12 indicates it has data to transmit, the clientstation 12 remains active. Otherwise, the client station 12 enters thelow power mode again.

The AP 14 attempts to transmit a beacon at a target beacon transmissiontime (TBTT). Before the AP 14 sends out a beacon transmission, the AP 14determines whether other devices are currently transmitting data so thatother devices are able to use the network. The client station 12transitions to the active mode prior to a beacon transmission to queueframes to transmit to the AP 14 in a buffer. Immediately following abeacon transmission, the AP 14 can exchange frames with one or moreclient stations 12 in a deterministic order. For example, the AP 14 andthe clients stations 12 may exchange data according to Time DivisionMultiplexed (TDM) protocol. The use of TDM protocol minimizes collisionsthat may occur when one or more of the client stations 12 attempt totransmit data to the AP 14 simultaneously. However, other wirelessnetworks that are located near the first wireless network 10 may notoperate according to the above-described TDM protocol. As such,collisions may occur between the other wireless networks and the firstwireless network 10.

In another implementation, each client station 12 may wait for a randomperiod prior to transmitting. This random period, or backoff period,reduces the likelihood that multiple client stations will attempt totransmit simultaneously. As such, a wireless network that implements therandom backoff period has improved collision avoidance over a wirelessnetwork that implements a pure TDM scheme when multiple networks existin an overlapping region. However, random backoff but does not guaranteecollision avoidance. In certain applications, collision avoidance iscritical. For example, wireless networks that exchange multicast datatypically do not include a positive acknowledgement feature. In otherwords, a transmitting station does not receive acknowledgement from areceiving station that the data was correctly received. Further, as aresult of the random backoff periods, the time required for all stationsin the wireless network to complete a set of frame exchanges isincreased.

Referring now to FIG. 2, a second wireless network 24 operates in anad-hoc mode. The second wireless network 24 includes multiple clientstations 26-1, 26-2, and 26-3 that transmit and receive wireless signals28. The client stations 26-1, 26-2, and 26-3 collectively form a LAN andcommunicate directly with each other. The client stations 26-1, 26-2,and 26-3 are not necessarily connected to another network. The clientstations 26-1, 26-2, and 26-3 do not continuously transmit data to andreceive data from each other. The client stations 26 implement a powersavings mode when one of the client stations 26-1 does not have data toexchange with the other client stations 26-2 and 26-3.

The client stations 26-1, 26-2, and 26-3 are not required to buffer dataas performed in the AP. For example, the client station 26-1 transmitsthe beacon to the other client stations 26-2 and 26-3. The clientstations 26-2 and 26-3 transition to the active mode prior to the beacontransmission. During a beacon interval defined by the beacontransmission, each client station 26 transmits data in a deterministicorder. For example, the client stations 26 may transmit datasequentially.

SUMMARY OF THE INVENTION

A wireless network device comprises an RF transceiver that transmits andreceives data packets and that periodically transmits or receives abeacon. A control module communicates with the RF transceiver,determines a default interframe space (IFS) time based on the beacon,and that selects one of the default IFS time and a second IFS time thatis less than or equal to the default IFS time based on a number of datapackets received after the beacon.

In other features, the beacon includes data that is indicative of atransmission position m for the wireless network device. The controlmodule selects the second IFS time when the RF transceiver receives m−1data packets. The control module selects the default IFS time when theRF transceiver has received fewer than m−1 data packets.

In still other features, the control module includes an IFS timer thatis reset when data packets are received. The RF transceiver transmits adata packet after one of the default IFS time and the second IFS time. Apower management module that transitions the wireless network devicebetween an active mode and an inactive mode. The power management moduletransitions the wireless network device to the active mode prior to ascheduled beacon time. The power management module transitions thewireless network device to the inactive mode after the RF transceivertransmits a data packet. A wireless network comprising the wirelessnetwork device further comprises N−1 other wireless network devices. Thepower management module transitions the wireless network device to theinactive mode after all of the N wireless network devices transmit adata packet.

In still other features, a wireless network comprises a plurality of thewireless network devices. The power management module transitions thewireless network devices to the inactive mode after an idle time on thenetwork that is greater than a largest available IFS time. One of thewireless network devices is a coordinator that periodically transmitsthe beacon to the plurality of wireless network devices.

In other features, a wireless network device comprises transmitting andreceiving means for transmitting and receiving data packets and forperiodically transmitting or receiving a beacon. The wireless networkdevice comprises control means for communicating with the transmittingand receiving means, for determining a default interframe space (IFS)time based on the beacon, and for selecting one of the default IFS timeand a second IFS time that is less than or equal to the default IFS timebased on a number of data packets received after the beacon.

In still other features, the beacon includes data that is indicative ofa transmission position m for the wireless network device. The controlmeans selects the second IFS time when the transmitting and receivingmeans receives m−1 data packets. The control means selects the defaultIFS time when the transmitting and receiving means has received fewerthan m−1 data packets. The control means includes timing means formonitoring IFS times. The timing means is reset when data packets arereceived and the transmitting and receiving means transmits a datapacket after one of the default IFS time and the second IFS time.

In still other features, the wireless network device further comprisespower management means for transitioning the wireless network devicebetween an active mode and an inactive mode. The power management meanstransitions the wireless network device to the active mode prior to ascheduled beacon time. The power management means transitions thewireless network device to the inactive mode after the transmitting andreceiving means transmits a data packet.

In still other features, a wireless network comprising the wirelessnetwork device further comprises N−1 other wireless network devices. Thepower management means transitions the wireless network device to theinactive mode after all of the N wireless network devices transmit adata packet. The power management means transitions the wireless networkdevices to the inactive mode after an idle time on the network that isgreater than a largest available IFS time. One of the wireless networkdevices is a coordinator that periodically transmits the beacon to theplurality of wireless network devices.

In other features, a method for transmitting and receiving data with awireless network device comprises at least one of transmitting andreceiving data packets, at least one of periodically receiving andtransmitting a beacon, determining a default interframe space (IFS) timebased on the beacon, and selecting one of the default IFS time and asecond IFS time that is less than or equal to the default IFS time basedon a number of data packets received after the beacon.

In still other features, the step of selecting includes selecting thesecond IFS time after receiving m−1 data packets. The step of selectingincludes selecting the default IFS time when fewer than m−1 data packetsare received. An IFS timer is reset when data packets are received and adata packet is transmitted after one of the default IFS time or thesecond IFS time.

In other features, a computer program executed by a processor comprisesat least one of transmitting and receiving data packets, at least one ofperiodically receiving and transmitting a beacon, determining a defaultinterframe space (IFS) time based on the beacon, and selecting one ofthe default IFS time and a second IFS time that is less than or equal tothe default IFS time based on a number of data packets received afterthe beacon.

In still other features, the beacon includes data that is indicative ofa transmission position m for a wireless network device. The step ofselecting includes selecting the second IFS time after receiving m−1data packets. The step of selecting includes selecting the default IFStime when fewer than m−1 data packets are received. An IFS timer isreset when data packets are received and a data packet is transmittedafter one of the default IFS time or the second IFS time.

In still other features, the wireless network device is transitionedbetween an active mode and an inactive mode. The step of transitioningincludes transitioning the wireless network device to the active modeprior to a scheduled beacon time. The step of transitioning includestransitioning the wireless network device to the inactive mode aftertransmitting a data packet. The wireless network device is transitionedto the inactive mode after N wireless network devices transmit a datapacket, wherein N is a number of wireless network devices in a wirelessnetwork including the wireless network device. The wireless networkdevice is transitioned to the inactive mode after an idle time on awireless network including the wireless network device that is greaterthan a largest available IFS time. The beacon is transmitted to aplurality of wireless network devices.

In other features, a first wireless network device in a wireless networkthat includes a plurality of wireless network devices comprises an RFtransceiver that transmits and receives data packets and thatperiodically transmits or receives a beacon. A control modulecommunicates with the RF transceiver, determines a transmission positionm and a default IFS time based on the beacon, selects a second IFS timewhen the RF transceiver receives a data packet from a second wirelessnetwork device having a transmission position m−1, and selects thedefault IFS time when the RF transceiver does not receive a data packetfrom the second wireless network device.

In still other features, the second IFS time is less than or equal tothe default IFS time. The RF transceiver transmits a data packet afterone of the default IFS time or the second IFS time. A power managementmodule transitions the wireless network device between an active modeand an inactive mode. The power management module transitions thewireless network device to the active mode prior to a scheduled beacontime. The power management module transitions the wireless networkdevice to the inactive mode after the RF transceiver transmits the datapacket.

In still other features, a wireless network comprising the wirelessnetwork device further comprises N−1 wireless network devices. The powermanagement module transitions the wireless network device to theinactive mode after all of the N wireless network devices transmit adata packet. A coordinator device periodically transmits the beacon tothe RF transceiver. The transmission position m=2 and the second IFStime is equal to a default IFS time of the second wireless networkdevice.

In other features, a first wireless network device in a wireless networkthat includes a plurality of wireless network devices comprisestransmitting and receiving means for transmitting and receiving datapackets and for periodically transmitting or receiving a beacon, andcontrol means for communicating with the transmitting and receivingmeans, for determining a transmission position m and a default IFS timebased on the beacon, for selecting a second IFS time when thetransmitting and receiving means receives a data packet from a secondwireless network device having a transmission position m−1, and forselecting the default IFS time when the transmitting and receiving meansdoes not receive a data packet from the second wireless network device.

In still other features, the second IFS time is less than or equal tothe default IFS time. The RF transceiver transmits a data packet afterone of the default IFS time or the second IFS time. The wireless networkdevice further comprises power management means for transitioning thewireless network device between an active mode and an inactive mode. Thepower management means transitions the wireless network device to theactive mode prior to a scheduled beacon time. The power management meanstransitions the wireless network device to the inactive mode after theRF transceiver transmits the data packet.

In still other features, a wireless network comprising the wirelessnetwork device of further comprises N−1 wireless network devices. Thepower management means transitions the wireless network device to theinactive mode after all of the N wireless network devices transmit adata packet. The transmission position m=2 and the second IFS time isequal to a default IFS time of the second wireless network device.

In other features, a method for transmitting and receiving data with afirst wireless network device in a wireless network that includes aplurality of wireless network devices comprises transmitting andreceiving data packets, periodically transmitting or receiving a beacon,determining a transmission position m and a default IFS time based onthe beacon, selecting a second IFS time when the first wireless networkdevice receives a data packet from a second wireless network devicehaving a transmission position m−1, and selecting the default IFS timewhen the first wireless network device does not receive a data packetfrom the second wireless network device.

In still other features, the second IFS time is less than or equal tothe default IFS time. A data packet is transmitted after one of thedefault IFS time or the second IFS time. The first wireless networkdevice is transitioned between an active mode and an inactive mode. Thestep of transitioning includes transitioning the first wireless networkdevice to the active mode prior to a scheduled beacon time. The step oftransitioning includes transitioning the first wireless network deviceto the inactive mode after the first wireless network device transmitsthe data packet.

In still other features, the wireless network includes N wirelessnetwork devices. The first wireless network device is transitioned tothe inactive mode after all of the N wireless network devices transmit adata packet. The transmission position m=2 and the second IFS time isequal to a default IFS time of the second wireless network device.

In other features, a computer program executed by a processor comprisestransmitting and receiving data packets, periodically transmitting orreceiving a beacon, determining a transmission position m and a defaultIFS time based on the beacon, selecting a second IFS time when a firstwireless network device receives a data packet from a second wirelessnetwork device having a transmission position m−1, and selecting thedefault IFS time when the first wireless network device does not receivea data packet from the second wireless network device.

In still other features, the second IFS time is less than or equal tothe default IFS time. A data packet is transmitted after one of thedefault IFS time or the second IFS time. The first wireless networkdevice is transitioned between an active mode and an inactive mode. Thestep of transitioning includes transitioning the first wireless networkdevice to the active mode prior to a scheduled beacon time. The step oftransitioning includes transitioning the first wireless network deviceto the inactive mode after the first wireless network device transmitsthe data packet. The transmission position m=2 and the second IFS timeis equal to a default IFS time of the second wireless network device.

In other features, a wireless network device in a wireless network thatincludes a plurality of wireless network devices comprises an RFtransceiver that transmits and receives data packets and thatperiodically transmits or receives a beacon. A control modulecommunicates with the RF transceiver, determines a group identifier anda station identifier based on the beacon, and selects one of a defaultIFS time and a second IFS time based on a data packet received.

In still other features, the control module selects one of the defaultIFS time and the second IFS time based on the data packet received andat least one of the group identifier and/or the station identifier. Thesecond IFS time is less than or equal to the default IFS time. Thecontrol module determines a group identifier x and a station identifiery based on the beacon. The control module selects the second IFS timewhen the data packet is received from a second wireless network devicehaving a group identifier x−1 and a station identifier y. The controlmodule selects the second IFS time when the data packet is received froma second wireless network device having a group identifier less than xand a station identifier y. The control module selects the default IFStime when the data packet is received from a second wireless networkdevice having a group identifier x and a station identifier other thany.

In still other features, a group IFS time is based on the groupidentifier, a delta IFS time is based on the station identifier, and thedefault IFS time is a sum of the group IFS time and the delta IFS time.The device transmits a data packet after one of the default IFS time orthe second IFS time. A power management module that transitions thewireless network device between an active mode and an inactive mode. Thepower management module transitions the wireless network device to theactive mode prior to a scheduled beacon time. The power managementmodule transitions the wireless network device to the inactive modeafter the RF transceiver transmits the data packet. A coordinator deviceperiodically transmits the beacon to the RF transceiver.

In other features, a wireless network device in a wireless network thatincludes a plurality of wireless network devices comprises transmittingand receiving means for transmitting and receiving data packets and forperiodically transmitting or receiving a beacon and control means forcommunicating with the transmitting and receiving means, for determininga group identifier and a station identifier based on the beacon, and forselecting one of a default IFS time and a second IFS time based on adata packet received.

In still other features, the control means selects one of the defaultIFS time and the second IFS time based on the data packet received andat least one of the group identifier and/or the station identifier. Thesecond IFS time is less than or equal to the default IFS time. Thecontrol means determines a group identifier x and a station identifier ybased on the beacon. The control means selects the second IFS time whenthe data packet is received from a second wireless network device havinga group identifier x−1 and a station identifier y. The control meansselects the second IFS time when the data packet is received from asecond wireless network device having a group identifier less than x anda station identifier y. The control means selects the default IFS timewhen the data packet is received from a second wireless network devicehaving a group identifier x and a station identifier other than y.

In still other features, a group IFS time is based on the groupidentifier, a delta IFS time is based on the station identifier, and thedefault IFS time is a sum of the group IFS time and the delta IFS time.The device transmits a data packet after one of the default IFS time orthe second IFS time. The wireless network device further comprises powermanagement means for transitioning the wireless network device betweenan active mode and an inactive mode. The power management meanstransitions the wireless network device to the active mode prior to ascheduled beacon time. The power management means transitions thewireless network device to the inactive mode after the device transmitsthe data packet.

In other features, a method for transmitting and receiving data with afirst wireless network device in a wireless network that includes aplurality of wireless network devices comprises transmitting andreceiving data packets, periodically transmitting or receiving a beacon,determining a group identifier and a station identifier based on thebeacon, and selecting one of a default IFS time and a second IFS timebased on a data packet received.

In still other features, the step of selecting includes selecting one ofthe default IFS time and the second IFS time based on the data packetreceived and at least one of the group identifier and/or the stationidentifier. The second IFS time is less than or equal to the default IFStime. A group identifier x and a station identifier y are determinedbased on the beacon. The step of selecting includes selecting the secondIFS time when the data packet is received from a second wireless networkdevice having a group identifier x−1 and a station identifier y. Thestep of selecting includes selecting the second IFS time when the datapacket is received from a second wireless network device having a groupidentifier less than x and a station identifier y. The step of selectingincludes selecting the default IFS time when the data packet is receivedfrom a second wireless network device having a group identifier x and astation identifier other than y.

In still other features, a group IFS time is based on the groupidentifier, a delta IFS time is based on the station identifier, and thedefault IFS time is a sum of the group IFS time and the delta IFS time.A data packet is transmitted after one of the default IFS time or thesecond IFS time. The first wireless network device is transitionedbetween an active mode and an inactive mode. The step of transitioningincludes transitioning the first wireless network device to the activemode prior to a scheduled beacon time. The step of transitioningincludes transitioning the wireless network device to the inactive modeafter transmitting the data packet.

In other features, a computer program executed by a processor comprisestransmitting and receiving data packets, periodically transmitting orreceiving a beacon, determining a group identifier and a stationidentifier based on the beacon, and selecting one of a default IFS timeand a second IFS time based on a data packet received.

In still other features, the step of selecting includes selecting one ofthe default IFS time and the second IFS time based on the data packetreceived and at least one of the group identifier and/or the stationidentifier. The second IFS time is less than or equal to the default IFStime. A group identifier x and a station identifier y are determinedbased on the beacon. The step of selecting includes selecting the secondIFS time when the data packet is received from a wireless network devicehaving a group identifier x−1 and a station identifier y.

In still other features, the step of selecting includes selecting thesecond IFS time when the data packet is received from a wireless networkdevice having a group identifier less than x and a station identifier y.The step of selecting includes selecting the default IFS time when thedata packet is received from a wireless network device having a groupidentifier x and a station identifier other than y. A group IFS time isbased on the group identifier, a delta IFS time is based on the stationidentifier, and the default IFS time is a sum of the group IFS time andthe delta IFS time. A data packet is transmitted after one of thedefault IFS time or the second IFS time.

In still other features, a wireless network device is transitionedbetween an active mode and an inactive mode. The step of transitioningincludes transitioning the wireless network device to the active modeprior to a scheduled beacon time. The step of transitioning includestransitioning the wireless network device to the inactive mode aftertransmitting the data packet.

In still other features, the systems and methods described above areimplemented by a computer program executed by one or more processors.The computer program can reside on a computer readable medium such asbut not limited to memory, non-volatile data storage and/or othersuitable tangible storage mediums.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred embodiment of the invention, are intended forpurposes of illustration only and are not intended to limit the scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a functional block diagram of a wireless network that isconfigured in an infrastructure mode and that includes one or moreclient stations and an access point (AP) according to the prior art;

FIG. 2 is a functional block diagram of a wireless network that isconfigured in an ad-hoc mode and that includes multiple client stationsaccording to the prior art;

FIG. 3 is a functional block diagram of a wireless gaming network thatis configured in an infrastructure mode wireless local area network(LAN) according to the present invention;

FIG. 4 is a functional block diagram of an AP for a console in awireless gaming network that includes an SOC and a radio frequency (RF)transceiver according to the present invention;

FIG. 5 is a functional block diagram of a wireless network deviceaccording to the present invention;

FIG. 6 is a timing diagram that illustrates client station TDM protocoldelta times in a wireless LAN according to the prior art;

FIG. 7A is a timing diagram that illustrates client station IFS times ina wireless LAN according to a first implementation of the presentinvention;

FIG. 7B is a timing diagram that illustrates client station IFS times ina wireless LAN according to a first implementation of the presentinvention;

FIG. 7C is a timing diagram that illustrates client station IFS times ina wireless LAN according to a first implementation of the presentinvention;

FIG. 7D is a timing diagram that illustrates client station IFS times ina wireless LAN according to a first implementation of the presentinvention;

FIG. 8 is a flowchart that illustrates steps performed by a wirelessnetwork device to select client station IFS times according to a firstimplementation of the present invention.

FIG. 9A is a timing diagram that illustrates client station IFS times ina wireless LAN according to a second implementation of the presentinvention;

FIG. 9B is a timing diagram that illustrates client station IFS times ina wireless LAN according to a second implementation of the presentinvention;

FIG. 9C is a timing diagram that illustrates client station IFS times ina wireless LAN according to a second implementation of the presentinvention;

FIG. 10 is a flowchart that illustrates steps performed by a wirelessnetwork device to select client station IFS times according to a secondimplementation of the present invention;

FIG. 11A is a timing diagram that illustrates client station IFS timesin a wireless LAN according to a third implementation of the presentinvention;

FIG. 11B is a timing diagram that illustrates client station IFS timesin a wireless LAN according to a third implementation of the presentinvention;

FIG. 11C is a timing diagram that illustrates client station IFS timesin a wireless LAN according to a third implementation of the presentinvention;

FIG. 11D is a timing diagram that illustrates client station IFS timesin a wireless LAN according to a third implementation of the presentinvention;

FIG. 12 is a flowchart that illustrates steps performed by a wirelessnetwork device to select client station IFS times according to a thirdimplementation of the present invention;

FIG. 13A is a functional block diagram of a high definition television;

FIG. 13B is a functional block diagram of a vehicle control system;

FIG. 13C is a functional block diagram of a cellular phone; and

FIG. 13D is a functional block diagram of a set top box.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses. For purposes of clarity, the same referencenumbers will be used in the drawings to identify similar elements. Asused herein, the term module and/or device refers to an applicationspecific integrated circuit (ASIC), an electronic circuit, a processor(shared, dedicated, or group) and memory that execute one or moresoftware or firmware programs, a combinational logic circuit, and/orother suitable components that provide the described functionality.

An inter-frame space (IFS) time is a minimum time that a station waitsafter the communication medium becomes free prior to transmitting data.To minimize power consumption, the wireless protocol according to thepresent invention allows stations to use shorter and/or constant IFStimes with no random backoff periods. By preventing collisions whileeliminating the need for random backoff periods and by maintaining shortIFS times for every station, the average awake time and the powerconsumption of all of the stations is reduced. A wireless networkoperating in either an infrastructure mode or an ad hoc mode mayimplement the wireless protocol as described herein.

In some types of networks, most or all of the stations need to transmitdata regularly, for example, at each beacon interval. One example ofthis type of network is a wireless console gaming application. Sincemost or all of the stations transmit frames to one or more otherstations during each beacon interval, a master station determines astation access sequence after each beacon transmission. The masterstation can vary the station access sequence by randomizing or rotatingthe order following each beacon transmission. The IFS time for eachstation is dependent partly upon the access sequence and partly uponframes previously received in a particular beacon period. In thismanner, a given client station will transmit data according to a firstIFS time during a first beacon interval, and according to a second ordifferent IFS time during a second beacon interval.

In a wireless gaming network operating in the infrastructure or ad hocmode, all client stations transmit frames to every other client stationduring each beacon interval. The IFS times of each client stationdictate a client access sequence for a given beacon interval. The clientstation access sequence is varied by randomizing or rotating the IFStimes among the client stations following each beacon transmission. Inthis manner, a given client station will transmit data according to afirst IFS time during a first beacon interval, and according to a secondIFS time during a second beacon interval.

Referring now to FIG. 3, a wireless gaming network 30 includes a hostgaming device 32 and one or more client gaming devices 34. The clientgaming devices 34 include wireless local area network (WLAN) hardwareand operate as client stations in an infrastructure mode network. Thehost gaming device 32 also includes wireless LAN hardware and operatesas an access point (AP) in the wireless gaming network. The wirelessgaming network allows for greater mobility of the client gaming devices34 and conserves operating power by reducing the overall duration of theactive mode. Those skilled in the art can appreciate that the hostgaming device 32 and the client gaming devices 34 may be a game consoleand wireless input devices, respectively, or any other suitableimplementation of an AP and one or more wireless client stations.Alternatively, the wireless gaming network 30 excludes the host gamingdevice 32 and operates in an ad hoc mode.

Referring now to FIG. 4, an exemplary AP 14 for a host gaming device 32includes a system on chip (SOC) 34. The SOC 34 includes a basebandprocessor (BBP) 42, a media access control (MAC) device 44, and otherSOC components, identified collectively at 46, including interfaces,memory, and/or processors. A radio frequency (RF) transceiver 48 alongwith the BBP 42 communicates with the MAC device 44. The RF transceiver48 transmits/receives data to/from client stations in the wireless LAN.Since the AP 14 may have data that is intended for the client stationsduring the low power mode, the MAC device 44 includes a buffer 50. TheMAC device 44 stores data that is intended for the client stations inthe buffer 50 until the client stations enter the active mode. Asillustrated in FIG. 1, the AP 14 may be a node in a network 18 thatincludes other nodes such as a server 20 and may be connected to adistributed communications system 22 such as the Internet.

Each client gaming device 34 includes an exemplary wireless networkdevice 60 as shown in FIG. 5. The wireless network device 60 accordingto some implementations of the present invention is shown to include anRF transceiver module 62, a baseband processor module 64, a power andclock module 66, a MAC module 68, and a power management module 70. TheRF transceiver 62 includes a receiver 72 and a transmitter 74. While notshown, the network device 60 can also include a processor and otherstandard components.

A frequency synthesizer 76 includes a phase locked loop (PLL) 78 thatreceives a first reference frequency from an oscillator such as acrystal oscillator 80. The frequency synthesizer 76 also contains avoltage controlled oscillator (VCO) 82, which provides an adjustablefrequency output based on an input signal thereto. The frequencysynthesizer 76 generates RF and IF output signals for the receiver andtransmitter 72 and 74, respectively.

During receiver operation, an input of a low noise amplifier (LNA) 84receives signals from an antenna (not shown), amplifies the signals andoutputs them to the receiver 72. During transmitter operation, an outputof the transmitter 74 is received by a power amplifier (PA) 86, whichoutputs amplified signals to the antenna.

On the receiver side, the BBP 64 includes an analog to digital converter(ADC) 88 that receives signals from the receiver 72. The ADC 88communicates with a demodulator 90, which demodulates the signals. Anoutput of the demodulator 90 communicates with an external interface 92,which communicates with the MAC 68. On the transmitter side, the MAC 68sends signals to the external interface 92, which are modulated by amodulator 94 and output to a digital to analog converter (DAC) 96. TheDAC 96 outputs signals to the transmitter 74. The BBP 64 also mayinclude a PLL (not shown). Alternatively, the ADC 88 and the DAC 96 maybe located on the RF transceiver 62.

The power and clock module 66 includes a multi-level voltage source 98that receives an input voltage such as VDD and a mode signal and outputstwo or more voltage levels. The power and clock module 66 also includesa low power (LP) oscillator 100. The power management module 70 alongwith the MAC module 68 and processor (not shown) selects an operatingmode of the wireless network device 60. The operating modes includeactive and inactive (i.e. low power) modes, although additional modesmay be provided. The power management module 70 may also be located inthe MAC module 68 or the power and clock module 66.

An optional calibration module 102 that is associated with the powermanagement module 70 is optionally used to calibrate the duration of theinactive mode. The calibration module 102 receives an output of the LPoscillator 100 and a PLL 104 and calibrates a value of a counter 106that is used to calculate the duration of the inactive mode. Thecalibration can be performed periodically, on an event basis, randomly,before transitioning to the inactive mode and/or on any other suitablebasis. Alternatively, the calibration module 102 may be omitted from thewireless network device 60.

The power and clock module 66 further includes current and voltage biascircuits 108 and 110, respectively, that provide current and/or voltagebiases to various circuits and/or modules (connections not shown) in thewireless network device 60. The current bias circuit 108 may include oneor more off-chip calibration resistors (not shown) and the voltage biascircuit may include one or more on-chip resistors (not shown). A bandgap voltage reference 112 may be used to bias the current bias circuit108.

A clock data recovery (CDR) module 114 performs clock recovery andincludes analog and digital modules 116 and 118, respectively, or onlydigital modules. An output of the phase lock loop (PLL) 104 is coupledto the CDR module 114.

Referring to now FIG. 6, an exemplary TDM timing diagram 120 accordingto the prior art is illustrated. One or more client stations enter theactive mode prior to the transmission of a beacon signal 122. In awireless network operating in the infrastructure mode, the AP transmitsthe beacon signal 122. In the ad hoc mode, however, one of the clientstations transmits the beacon signal. The client stations attempt totransmit data according to assigned delay times following the receptionof the beacon and during an awake interval 124 that is defined by thebeacon signal 122.

Delay, or delta, times for each client station can be varied each beaconinterval. For example, the default delay times may be carried in thebeacon signal 122. As a result, the station access sequence for theclient stations varies with each beacon interval. The client stationswait the delay time after the transmission medium becomes free beforetransmitting data. When transmission of a data frame or packet over themedium is complete, the device that receives the data packet maytransmit an acknowledgment data packet if the destination of the packetis a single receiver.

A first client station waits a first delta time 1 as illustrated at 126.Second, third, and nth client stations begin waiting second, third, . .. , and nth delta times, respectively. Since the delta time 1 is theshortest, it terminates first. The first client station transmits a datapacket as illustrated at 128. While the first client station transmits adata packet at 128, the remaining client stations are still waiting fortheir corresponding delta times. In other words, the transmission of thefirst client station at 128 occurs while the remaining client stationsare still waiting for their respective delta times to expire. Therefore,the second client station waits the second delta time 2 (the nextshortest delta time) as illustrated at 130. The second client stationthen transmits a data packet as illustrated at 132. The third clientstation waits the third delta time 3 as illustrated at 134, and thentransmits a data packet as illustrated at 136. The nth client stationwaits the nth delta time n as illustrated at 138, and then transmits adata packet as illustrated at 139.

In subsequent beacon intervals (not shown), the delta times of eachstation can be varied. For example, the nth client station may operateaccording to the first delta time 1, and the first client station mayoperate according to the third delta time 3. Similarly, the delta timesof the remaining client stations are varied. Those skilled in the artcan appreciate that the delta times, and therefore the station accesssequence, may be varied sequentially, randomly, or in any other suitablemanner.

The client stations transition to the low power mode after all clientstations complete transmission as illustrated by the termination of theawake interval 124. For example, in a wireless gaming network operatingin the infrastructure or ad hoc mode, each client station remains awakein order to receive all data packets from other client stations in thenetwork.

Alternatively, each client station transitions to the low power modeimmediately after transmitting a data packet. For example, in a wirelessgaming console operating in the infrastructure mode, wireless inputdevices operating as client stations may transition to the low powermode immediately after transmitting data to the console (AP). Since thestation access sequence varies following each beacon interval, thefirst, second, third, and nth client stations consume approximately thesame average power over time.

Referring now to FIGS. 7A through 7D, a timing diagram 140 illustrates afirst implementation of the present invention. Each client station isassigned a default unique IFS time 1, 2, 3, . . . , n as opposed to theunique delta times described with respect to FIG. 6. The unique IFStimes cause the stations to transmit in the order of ascending IFS,similar to the effect of the delta times described in FIG. 6. However,the IFS times measure a time since the transmission media becomes freerather than a fixed time since the beacon transmission 122. In thismanner, each client station waits a unique IFS time after the beacontransmission 122 and/or after a previous client station completestransmission.

The client stations follow one or more rules during each beacon intervalto determine whether to wait the assigned default IFS time or a shorteralternative IFS time. In one implementation, if a client stationreceives an expected number of data packets of a particular type (i.e.all preceding client stations have transmitted), then that clientstation waits the alternative IFS time. In typical wireless gamingapplications, each client station has a single data packet to transmitto all other client stations. However, a client station may have morethan one data packet type to transmit during a beacon interval. Forexample, a client gaming device may transmit a control data packet to ahost gaming device, and then transmit a gaming data packet to all otherclient gaming devices. Therefore, subsequent client gaming devices wouldexpect to receive the gaming data packet, but not the control datapacket.

Referring now to FIG. 7A, if a given client station receives datapackets from all previously transmitting client stations, the clientstation waits the IFS time 1. The IFS time 1 is the default IFS time ofthe first client station as illustrated at 142. The first client stationwaits the first IFS time 1 and transmits a data packet as illustrated at144. The second client station is second in the station access sequenceaccording to the IFS time 2, and therefore only expects to receive thedata packet from the first client station (i.e. one data packet of anexpected type) prior to transmitting. If the second client stationreceives the data packet from the first client station, the secondclient station waits the IFS time 1 as illustrated at 146, and transmitsa data packet as illustrated at 148.

In other words, because the first client station already transmitteddata during this beacon interval, there is no danger that collision willoccur between the first client station and the second client station atIFS time 1. The third client station is third in the station accesssequence, and therefore expects to receive two data packets prior totransmitting. If the third client station receives the data packets fromthe first and second client stations, the third client station waits theIFS time 1 as illustrated at 150 and transmits a data packet asillustrated at 152. The nth client station operates analogously andwaits the IFS time 1 as illustrated at 154 before transmitting a datapacket as illustrated at 156. In subsequent beacon intervals, the IFStimes are varied as described above, but the clients stations continueto follow the one or more rules for alternative IFS times.

In this manner, data is exchanged between all client stations morequickly, and the overall awake time of the client stations is reduced,minimizing power consumption. Additionally, since the percentage of timerequired for all stations to transmit their data is reduced, there is agreater likelihood that all stations will be able to transmit eachbeacon interval when competing for the medium with other WLAN networks.As described above and in FIG. 7A, the awake interval 124 issignificantly reduced if most or all client stations transmit andreceive properly.

Referring now to FIG. 7B, the timing diagram 140 illustrates operationof the client stations when one client station does not receive a datapacket from a preceding client station. The first client stationtransmits a data packet after IFS time 1 as illustrated at 158. However,the second client station does not properly receive the data packet fromthe first client station. For example, the second client station may notreceive the data packet due to noise or other network problems.Therefore, the second client station waits the IFS time 2 as illustratedat 160 prior to transmitting a data packet as illustrated at 162. Thethird and nth client stations properly receive all preceding datapackets and wait the IFS time 1 prior to transmitting as illustrated at164 and 166, respectively.

Referring now to FIG. 7C, the timing diagram 140 illustrates operationof the client stations when client stations 3 and above do not receive adata packet from a preceding client station. The first client stationtransmits a data packet after the IFS time 1 as illustrated at 170. Thesecond client station receives the data packet and transmits after theIFS time 1 as illustrated at 172. The third and nth client stations donot receive the data packet from the second client station. For example,noise may corrupt the transmission from the second client station.Therefore, the third and nth client stations are not able to use IFStime 1, and use the default IFS times 3, and n, respectively.

Alternatively, the second client station may be absent from the networkand/or fail to transmit altogether as shown in FIG. 7D. The first clientstation transmits a data packet after the IFS time 1 as illustrated at174. The second client station does not transmit a data packet.Therefore, the third client station waits the default IFS time 3 afterthe first client station completes transmission as illustrated at 176.The third client station transmits a data packet after the IFS time 3 asillustrated at 178. Similarly, the nth client station waits the defaultIFS time n after an (n−1)th client station completes transmission asillustrated at 180, and then transmits a data packet as illustrated at182.

Referring now to FIG. 8, a first IFS time selection method 184 begins instep 186. In step 188, the client stations enter the active mode priorto receiving a beacon transmission. In step 190, the client stationsreceive the beacon signal. The beacon signal includes data thatdetermines the default IFS times of the client stations. In the presentimplementation, the beacon signal may also indicate a slot m within thestation access sequence for each client station. Alternatively, thebeacon signal may include a single value that indicates both the defaultIFS time and the slot m of each client station. For example, the beaconsignal may include a timer synchronization function (TSF) value thatindicates the default IFS time and/or the slot m of the client station.In step 192, a client station determines whether it received m−1 datapackets of the correct type. If true, the method 184 continues to step194. If false, the method 184 continues to step 196. In step 194, theclient station waits an alternative IFS time that is less than or equalto the default IFS time. In step 196, the client station waits thedefault IFS time.

In step 198, the client station determines whether the IFS time of step194 or step 196 is up. If true, the method 184 continues to step 200. Iffalse, the method 184 continues to step 201. In step 201, the clientstation determines whether the transmission medium is free. If true, themethod 184 returns to step 198. If false, the method 184 continues tostep 202. In step 202, the client station resets the IFS timer, and themethod 184 returns to step 192. In other words, the client stationcontinues to wait the IFS time for as long as the transmission medium isfree. If the client station detects activity on the transmission medium,the IFS timer resets.

In step 200, the client station transmits a data packet. In step 203,the method 184 determines whether the client station has received datapackets from all the other client stations in the wireless network,and/or whether the beacon interval will expire soon. If true, the method184 continues to step 206. If false, the method 184 returns to step 203until all packets are received. In other words, if all stations havecompleted transmission and/or the beacon interval is to expire soon, themethod 184 continues to step 206. Otherwise, the method 184 returns tostep 203 and the station waits while each client station attempts totransmit in this manner. In step 206, the client station enters theinactive mode. In step 207, the method 184 starts an inactive modetimer. In step 208, the method 184 determines whether the inactive modetimer is up. If true, the method 184 repeats for subsequent beaconintervals and returns to step 188. If false, the method 184 returns tostep 208.

Referring now to FIGS. 9A through 9C, the timing diagram 210 illustratesa second implementation of the present invention. If a client stationreceives a data packet of a particular type from the immediatelypreceding client station, the client station waits an alternative IFStime before transmitting data. If the client station does not receivethe particular data packet from the immediately preceding clientstation, the client station waits the default IFS time beforetransmitting data. In the present implementation, each client station inthe network maintains a table of MAC addresses for all other clientstations in the network. In other words, each client station is able toidentify the data packet received from an immediately preceding clientstation based on its MAC address. Additionally, each data packetincludes information that identifies its order in the station accesssequence. In this manner, a receiving client station is able todetermine if a particular data packet was transmitted by the immediatelypreceding client station.

If a given client station receives the data packet from the immediatelypreceding client station, the client station waits the IFS time 1. Ifall client stations receive the data packet from the correspondingimmediately preceding client station, all client stations wait the IFStime 1 as shown previously in FIG. 7A. Referring now to FIG. 9A, thetiming diagram 210 illustrates operation of the client stations when oneclient station does not receive a data packet from an immediatelypreceding client station. The first client station transmits a datapacket after IFS time 1 as illustrated at 212. However, the secondclient station does not properly receive the data packet from the firstclient station. Therefore, the second client station waits the IFS time2 prior to transmitting a data packet as illustrated at 214. The thirdclient station properly receives the data packet from the second clientstation, and the nth client station properly receives the data packetfrom an (n−1)th station. Therefore, the third client station and the nthclient station wait the IFS time 1 before transmitting data.

Referring now to FIG. 9B, the timing diagram 210 illustrates operationof the client stations when all subsequent client stations do notreceive a data packet from a preceding client station. The first clientstation transmits a data packet after IFS time 1 as illustrated at 216.The second, third, and nth client stations do not receive the datapacket from the first client station. The second client station waitsthe IFS time 2 prior to transmitting a data packet as illustrated at218. However, according to the present implementation, the third and nthclient stations do not need to receive the data packet from the firstclient station in order to use the IFS time 1. If the third clientstation properly receives the data packet from the second clientstation, the third client station uses IFS time 1. Likewise, if the nthclient station receives the data packet from the (n−1)th client station,the nth client station uses IFS time 1.

Referring now to FIG. 9C, the timing diagram 210 illustrates operationof the client stations when one client station stops transmitting ordisconnects from the wireless network. The first client stationtransmits a data packet after IFS time 1 as illustrated at 220. Thesecond client station does not transmit. Therefore, the third clientstation transmits a data packet after waiting the IFS time 3 asillustrated at 222. If the nth client station properly receives the datapacket from the (n−1)th client station, the nth client station uses IFStime 1.

As described above in FIGS. 9A through 9C, subsequent client stationswill use the alternative IFS time if the immediately preceding clientstation transmitted a particular data packet. However, in certainsituations, collision may occur. For example, if the first clientstation is not able to transmit a data packet, the second client stationwill transmit a data packet after IFS time 2. After the second clientstation transmits the data packet, the third client station will attemptto transmit a data packet after IFS time 1. However, the first clientstation will wait until the second client station completestransmission, and also attempt to transmit a data packet after IFS time1, resulting in collision. Therefore, although the implementationdescribed in FIGS. 9A through 9C provides significant improvement in anoise-free environment, it can be seen that operation in certainenvironments is undesirable.

Referring now to FIG. 10, a second IFS time selection method 224 beginsin step 226. In step 228, the client stations transition to the activemode prior to receiving a beacon transmission. In step 230, the clientstations receive the beacon signal. The beacon signal includes data thatdetermines the default IFS times of the client stations, whichdetermines the slot in the station access sequence for each clientstation. In step 232, a client station determines whether it received adata packet from the client station in slot m−1. If true, the method 224continues to step 234. If false, the method 224 continues to step 236.In step 234, the client station waits an alternative IFS time that isshorter than the default IFS time. In step 236, the client station waitsthe default IFS time.

In step 238, the client station determines whether the IFS time of step234 or step 236 is up. If true, the method 224 continues to step 240. Iffalse, the method 224 continues to step 241. In step 241, the clientstation determines whether the transmission medium is free. If true, themethod 224 returns to step 238. If false, the method 224 continues tostep 242. In step 242, the client station resets the IFS timer, and themethod 224 returns to step 232.

In step 240, the client station transmits a data packet. In step 243,the method 224 determines whether the client station has received datapackets from all other client stations in the wireless network, and/orwhether the beacon interval will expire soon. If true, the method 224continues to step 246. If false, the method 224 returns to step 243until all packets are received. In other words, if all stations havecompleted transmission and/or the beacon interval is to expire soon, themethod 224 continues to step 246. Otherwise, the method 224 returns tostep 243 and the station waits while each client attempts to transmit inthis manner. In step 246, the client station enters the inactive mode.In step 247, the method 224 starts an inactive mode timer. In step 248,the method 224 determines if the inactive mode timer is up. If true, themethod 224 repeats for subsequent beacon intervals and returns to step228. If false, the method 224 returns to step 248.

Referring now to FIGS. 11A through 11D, the timing diagram 250illustrates a third implementation of the present invention. The clientstations are divided into two or more groups, and each client stationwithin a group is assigned a default IFS time. In one implementation,the default IFS time for a particular client station is equal to a groupIFS time plus an incremental delta time to determine station accesssequence. Each group is assigned an IFS group number that determines agroup IFS time IFSG1, IFSG2, IFSG3, . . . , IFSGx. Each client stationin a particular group is assigned an IFS station number that determinesan incremental delta time Δ1, Δ2, Δ3, . . . , Δq. Therefore, each clientstation is associated with an IFS group number and an IFS stationnumber.

If a client station properly receives a data packet from a correspondingclient station of an immediately preceding group, the client stationuses the smallest IFS time of a corresponding client station from whichthe client station has properly received a data packet. In other words,if the client station is associated with IFS station 1, the clientstation uses the smallest IFS time of any preceding IFS station 1.

Referring to FIG. 11A, first and second client stations are stations 1and 2 of a first group and have default IFS times 1 and 2, respectively.The IFS time 1 is equivalent to a group IFS time IFSG1 plus anincremental delta time Δ1, and the IFS time 2 is equivalent to the groupIFS time IFSG1 plus an incremental delta time Δ2. Third and fourthclient stations are stations 1 and 2 of a second group and have defaultIFS times 3 and 4, respectively. The IFS time 3 is equivalent to a groupIFS time IFSG2 plus the incremental delta time Δ1, and the IFS time 4 isequivalent to the group IFS time IFSG2 plus the incremental delta timeΔ2. Fifth and sixth client stations are stations 1 and 2 of a thirdgroup and have default IFS times 5 and 6, respectively. The IFS time 5is equivalent to a group IFS time IFSG3 plus the incremental delta timeΔ1, and the IFS time 6 is equivalent to the group IFS time IFSG3 plusthe incremental delta time Δ2.

Each successive group IFS time is greater than the preceding group IFStime plus an incremental delta time Δq. For example, the group IFS timeIFSG2 is greater than the group IFS time IFSG1 time plus an incrementaldelta time Δq. Similarly, the group IFS time IFSG3 is greater than thegroup IFS time IFSG2 plus the incremental delta time Δq. In this manner,the client stations in subsequent groups have longer default IFS timesthan the client stations of preceding groups. Therefore, collisionsbetween client stations of different groups is avoided.

The first client station transmits a data packet after the IFS time 1 asillustrated at 252. As described above, the IFS time 1 is equivalent tothe group IFS time IFSG1 plus the incremental delta time Δ1 asillustrated at 253. The first, third, and fifth client stations are allassociated with IFS station number 1. Therefore, if the third clientstation receives the data packet from the first client station, thethird client station reuses the IFS time 1 of the first client stationas illustrated at 254. If the fifth client station receives the datapackets from the first and third client stations, the fifth clientstation reuses either the IFS time 1 or the IFS time 3, whichever issmaller. In the present example, the fifth client station reuses the IFStime 1 as illustrated at 256. The second client station transmits a datapacket after the IFS time 2 as illustrated at 258. The IFS time 2 isequivalent to the group IFS time IFSG1 plus the incremental delta timeΔ2 as illustrated at 259. The fourth client station receives the datapacket from the second client station and reuses the IFS time 2 of thesecond client station as illustrated at 260. The sixth client stationreceives the data packets from the second and fourth client stations,and therefore reuses the IFS time 2 or the IFS time 4. In the presentexample, the sixth client station reuses the IFS time 2 as illustratedat 262.

Referring now to FIG. 11B, the timing diagram 250 illustrates theoperation of the client stations in the event that a client station doesnot properly receive a data packet from a corresponding client stationin a preceding group. The first client station transmits a data packetafter the IFS time 1 as illustrated at 264. The third client stationreceives the data packet from the first client station and transmits adata packet after the IFS time 1 as illustrated at 266. The fifth clientstation receives the data packets from the first and third clientstations and transmits a data packet after the IFS time 1 as illustratedat 268. The second client station transmits a data packet after the IFStime 2 as illustrated at 270. The fourth client station does notproperly receive the data packet from the second client station.Therefore, the fourth client station is not able to reuse the IFS time 2of the second client station, and transmits a data packet after the IFStime 4 as illustrated at 272. The IFS time 4 is equivalent to the groupIFS time IFSG2 plus the incremental delta time Δ2 as illustrated at 273.The sixth client station receives the data packets from the secondclient station and the fourth client station. The sixth client stationis able to reuse either the IFS time 2 or the IFS time 4, whichever issmaller. Therefore, the sixth client station reuses the IFS time 2 asillustrated at 274.

Referring now to FIG. 11C, the timing diagram 250 illustrates theoperation of the client stations in the event that multiple clientstations do not properly receive a data packet from a correspondingclient station in a preceding group. In the present example, the fourth,fifth, and sixth client stations do not properly receive the data packetfrom the third client station. The first and third client stations usethe IFS time 1 as described above. However, the fifth client stationdoes not properly receive the data packet from the third client station,and therefore waits IFS time 5. The second client station waits IFS time2, which is shorter than IFS time 5. Therefore, the second clientstation preempts the fifth client station and transmits after IFS time 2as illustrated at 276. The fourth and sixth client stations reuse theIFS time 2 of the second client station. After the transmission mediumis free following the transmission from the sixth client station, thefifth client station transmits a data packet after IFS time 5 asillustrated at 278. The IFS time 5 is equivalent to the group IFS timeIFSG3 plus the incremental delta time Δ1 as illustrated at 279.

Referring now to FIG. 11D, the timing diagram 250 illustrates theoperation of the client stations in the event that one or more clientstations stop transmitting on the network. In the present example, thesecond client station is no longer transmitting data packets. The first,third, and fifth client stations transmit data packets after the IFStime 1 as described in previous examples. The fourth client station doesnot receive a data packet from the second client station, and thereforetransmits a data packet after the IFS time 4 as illustrated at 280. Thesixth client station receives the data packet from the fourth clientstation, and is able to reuse the IFS time 4 of the fourth clientstation as illustrated at 282.

Referring now to FIG. 12, a third IFS time selection method 290 beginsin step 292. In step 294, the client stations come awake prior toreceiving a beacon transmission. In step 296, the client stationsreceive the beacon signal. The beacon signal includes data thatdetermines group and station identification numbers for each clientstation as described with reference to FIGS. 11A through 11C, as well ascorresponding default IFS times according to the group IFS time plus theincremental delta time. Alternatively, the group and stationidentification numbers are pre-assigned. In step 298, a client stationdetermines whether it received data packets from one or more clientstations with a corresponding station identification number in apreceding group and received a data packet from the client station withthe corresponding station identification number in the immediatelypreceding group. If true, the method 290 continues to step 300. Iffalse, the method continues to step 302. In step 300, the client stationreuses the shortest IFS time of a preceding client station having thesame station identification number from which the client stationsuccessfully received a data packet. In step 302, the client stationwaits the default IFS time.

In step 304, the client station determines whether the IFS time of step300 or step 302 is up. If true, the method 290 continues to step 306. Iffalse, the method 290 continues to step 308. In step 308, the clientstation determines whether the transmission medium is free. If true, themethod 290 returns to step 304. If false, the method 290 continues tostep 310. In step 310, the client station resets the IFS timer, and themethod 290 returns to step 298.

In step 306, the client station transmits a data packet. In step 312,the method 290 determines whether the client station has received datapackets from all other client stations in the wireless network, and/orwhether the beacon interval will expire soon. If true, the method 290continues to step 318. If false, the method 290 returns to step 312until all packets are received. In other words, if all stations havecompleted transmission and/or the beacon interval is to expire soon, themethod 290 continues to step 318. Otherwise, the method 290 returns tostep 312 and each client station attempts to transmit in this manner. Instep 318, the client station enters the inactive mode. In step 320, themethod 290 starts an inactive mode timer. In step 322, the method 290determines whether the inactive mode timer is up. If true, the method290 repeats for subsequent beacon intervals and returns to step 294. Iffalse, the method 290 repeats step 322.

Those skilled in the art can appreciate that any suitableimplementations of the methods described in FIGS. 7 through 12 can becombined. In one implementation, referring to FIGS. 11A through 11D, asubsequent client station may automatically reuse the IFS time of thecorresponding client station from the immediately preceding group. Inanother implementation, a subsequent client station may reuse theshortest IFS time of any preceding client station provided that thesubsequent client station receives data packets from all precedingstations. However, if the subsequent station does not receives all datapackets, the subsequent station is still able to reuse the IFS time of acorresponding client station.

Referring now to FIGS. 13A-13D, various exemplary implementations of thepresent invention are shown. Referring now to FIG. 13A, the presentinvention can be implemented in a high definition television (HDTV) 420.In particular, the present invention may implement and/or be implementedin a WLAN interface of the HDTV 420. The HDTV 420 receives HDTV inputsignals in either a wired or wireless format and generates HDTV outputsignals for a display 426. In some implementations, signal processingcircuit and/or control circuit 422 and/or other circuits (not shown) ofthe HDTV 420 may process data, perform coding and/or encryption, performcalculations, format data and/or perform any other type of HDTVprocessing that may be required. The HDTV 420 includes a power supply423.

The HDTV 420 may communicate with mass data storage 427 that stores datain a nonvolatile manner such as optical and/or magnetic storage devices.The HDTV 420 may be connected to memory 428 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The HDTV 420 also may support connections witha WLAN via a WLAN network interface 429.

Referring now to FIG. 13B, the present invention may implement and/or beimplemented in a WLAN interface of control system of a vehicle 430. Insome implementations, the present invention implements a powertraincontrol system 432 that receives inputs from one or more sensors such astemperature sensors, pressure sensors, rotational sensors, airflowsensors and/or any other suitable sensors and/or that generates one ormore output control signals such as engine operating parameters,transmission operating parameters, and/or other control signals. Thevehicle 430 includes a power supply 433.

The present invention may also be implemented in other control systems440 of the vehicle 430. The control system 440 may likewise receivesignals from input sensors 442 and/or output control signals to one ormore output devices 444. In some implementations, the control system 440may be part of an anti-lock braking system (ABS), a navigation system, atelematics system, a vehicle telematics system, a lane departure system,an adaptive cruise control system, a vehicle entertainment system suchas a stereo, DVD, compact disc and the like. Still other implementationsare contemplated.

The powertrain control system 432 may communicate with mass data storage446 that stores data in a nonvolatile manner. The mass data storage 446may include optical and/or magnetic storage devices. The powertraincontrol system 432 may be connected to memory 447 such as RAM, ROM, lowlatency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The powertrain control system 432 also maysupport connections with a WLAN via a WLAN network interface 448. Thecontrol system 440 may also include mass data storage, memory and/or aWLAN interface (all not shown).

Referring now to FIG. 13C, the present invention can be implemented in acellular phone 450 that may include a cellular antenna 451. The presentinvention may implement and/or be implemented in a WLAN interface of thecellular phone 450. In some implementations, the cellular phone 450includes a microphone 456, an audio output 458 such as a speaker and/oraudio output jack, a display 460 and/or an input device 462 such as akeypad, pointing device, voice actuation and/or other input device.Signal processing and/or control circuits 452 and/or other circuits (notshown) in the cellular phone 450 may process data, perform coding and/orencryption, perform calculations, format data and/or perform othercellular phone functions. The cellular phone includes a power supply453.

The cellular phone 450 may communicate with mass data storage 464 thatstores data in a nonvolatile manner such as optical and/or magneticstorage devices. The cellular phone 450 may be connected to memory 466such as RAM, ROM, low latency nonvolatile memory such as flash memoryand/or other suitable electronic data storage. The cellular phone 450also may support connections with a WLAN via a WLAN network interface468.

Referring now to FIG. 13D, the present invention can be implemented in aset top box 480. The present invention may implement and/or beimplemented in a WLAN interface of the set top box 480. The set top box480 receives signals from a source such as a broadband source andoutputs standard and/or high definition audio/video signals suitable fora display 488 such as a television and/or monitor and/or other videoand/or audio output devices. Signal processing and/or control circuits484 and/or other circuits (not shown) of the set top box 480 may processdata, perform coding and/or encryption, perform calculations, formatdata and/or perform any other set top box function. The set top box 480includes a power supply 483.

The set top box 480 may communicate with mass data storage 490 thatstores data in a nonvolatile manner. The mass data storage 490 mayinclude optical and/or magnetic storage devices such as hard disk drivesHDD and/or DVDs. The set top box 480 may be connected to memory 494 suchas RAM, ROM, low latency nonvolatile memory such as flash memory and/orother suitable electronic data storage. The set top box 480 also maysupport connections with a WLAN via a WLAN network interface 496.

While the present invention has been described in the context of IEEEstandards 802.11, 802.11a, 802.11b, 802.11g, 802.11h, 802.11n, 802.16,and 802.20, the present invention has application to other current andfuture wireless protocols.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the present invention can beimplemented in a variety of forms. Therefore, while this invention hasbeen described in connection with particular examples thereof, the truescope of the invention should not be so limited since othermodifications will become apparent to the skilled practitioner upon astudy of the drawings, the specification and the following claims.

1. A first wireless network device in a wireless network that includes aplurality of wireless network devices, comprising: an RF transceiverthat transmits and receives data packets and that periodically transmitsor receives a beacon; and a control module that communicates with the RFtransceiver, that determines a transmission position m and a default IFStime based on the beacon, that selects a second IFS time when the RFtransceiver receives a data packet from a second wireless network devicehaving a transmission position m−1, and that selects the default IFStime when the RF transceiver does not receive a data packet from thesecond wireless network device.
 2. The wireless network device of claim1 wherein the second IFS time is less than or equal to the default IFStime.
 3. The wireless network device of claim 1 wherein the RFtransceiver transmits a data packet after one of the default IFS time orthe second IFS time.
 4. The wireless network device of claim 3 furthercomprising a power management module that transitions the wirelessnetwork device between an active mode and an inactive mode.
 5. Thewireless network device of claim 4 wherein the power management moduletransitions the wireless network device to the active mode prior to ascheduled beacon time.
 6. The wireless network device of claim 5 whereinthe power management module transitions the wireless network device tothe inactive mode after the RF transceiver transmits the data packet. 7.A wireless network comprising the wireless network device of claim 4 andfurther comprising N−1 wireless network devices wherein the powermanagement module transitions the wireless network device to theinactive mode after all of the N wireless network devices transmit adata packet.
 8. A wireless network comprising the wireless networkdevice of claim 1 and further comprising a coordinator device thatperiodically transmits the beacon to the RF transceiver.
 9. The wirelessnetwork device of claim 1 wherein m=2 and the second IFS time is equalto a default IFS time of the second wireless network device.
 10. A firstwireless network device in a wireless network that includes a pluralityof wireless network devices, comprising: transmitting and receivingmeans for transmitting and receiving data packets and for periodicallytransmitting or receiving a beacon; and control means for communicatingwith the transmitting and receiving means, for determining atransmission position m and a default IFS time based on the beacon, forselecting a second IFS time when the transmitting and receiving meansreceives a data packet from a second wireless network device having atransmission position m−1, and for selecting the default IFS time whenthe transmitting and receiving means does not receive a data packet fromthe second wireless network device.
 11. The wireless network device ofclaim 10 wherein the second IFS time is less than or equal to thedefault IFS time.
 12. The wireless network device of claim 10 whereinthe transmitting and receiving means transmits a data packet after oneof the default IFS time or the second IFS time.
 13. The wireless networkdevice of claim 12 further comprising power management means fortransitioning the wireless network device between an active mode and aninactive mode.
 14. The wireless network device of claim 13 wherein thepower management means transitions the wireless network device to theactive mode prior to a scheduled beacon time.
 15. The wireless networkdevice of claim 14 wherein the power management means transitions thewireless network device to the inactive mode after the transmitting andreceiving means transmits the data packet.
 16. A wireless networkcomprising the wireless network device of claim 13 and furthercomprising N−1 wireless network devices wherein the power managementmeans transitions the wireless network device to the inactive mode afterall of the N wireless network devices transmit a data packet.
 17. Thewireless network device of claim 10 wherein m=2 and the second IFS timeis equal to a default IFS time of the second wireless network device.18. A method for transmitting and receiving data with a first wirelessnetwork device in a wireless network that includes a plurality ofwireless network devices, comprising: transmitting and receiving datapackets; periodically transmitting or receiving a beacon; determining atransmission position m and a default IFS time based on the beacon;selecting a second IFS time when the first wireless network devicereceives a data packet from a second wireless network device having atransmission position m−1; and selecting the default IFS time when thefirst wireless network device does not receive a data packet from thesecond wireless network device.
 19. The method of claim 18 wherein thesecond IFS time is less than or equal to the default IFS time.
 20. Themethod of claim 18 further comprising transmitting a data packet afterone of the default IFS time or the second IFS time.
 21. The method ofclaim 20 further comprising transitioning the first wireless networkdevice between an active mode and an inactive mode.
 22. The method ofclaim 21 wherein the step of transitioning includes transitioning thefirst wireless network device to the active mode prior to a scheduledbeacon time.
 23. The method of claim 22 wherein the step oftransitioning includes transitioning the first wireless network deviceto the inactive mode after the first wireless network device transmitsthe data packet.
 24. The method of claim 21 wherein the wireless networkincludes N wireless network devices, the method further comprisingtransitioning the first wireless network device to the inactive modeafter all of the N wireless network devices transmit a data packet. 25.The method of claim 18 wherein m=2 and the second IFS time is equal to adefault IFS time of the second wireless network device.